Add support of docker secrets

Related-Prod: PROD-35521
Related-Prod: PROD-34268
Change-Id: I45913ca9bbe84874e5d472094fbdfc8784fa39ea
diff --git a/README.rst b/README.rst
index f7a6313..de069f9 100644
--- a/README.rst
+++ b/README.rst
@@ -224,6 +224,40 @@
                   source: /srv/volumes/postgresql/maas
                   destination: /var/lib/postgresql/data
 
+Docker Service configuration samples with docker secrets
+========================================================
+
+To deploy service in Swarm mode using docker secrets, you can use
+``docker.client.service``:
+
+.. code-block:: yaml
+
+    parameters:
+      docker:
+        client:
+          service:
+            postgresql:
+              environment:
+                POSTGRES_USER: user
+                POSTGRES_PASSWORD_FILE: '/run/secrets/postgres'
+                POSTGRES_DB: mydb
+              secrets:
+                - postgres
+              restart:
+                condition: on-failure
+              image: "postgres:9.5"
+              ports:
+                - 5432:5432
+              volume:
+                data:
+                  type: bind
+                  source: /srv/volumes/postgresql/maas
+                  destination: /var/lib/postgresql/data
+          secrets:
+            postgres:
+              external: true
+              value: password
+
 Docker Registry configuration samples
 =====================================